1. Field of the Invention
The present invention relates to methods, compositions, and apparatus used to process algae and thereby extract various products such as lipids, proteins, carbohydrates, metabolites, and/or recombinant products from algae.
2. Description of Related Art
Algae, including microalgae, macroalgae, fresh water algae, and marine algae are potentially useful as sources of industrial, agricultural, and pharmaceutical products and their precursors.
WO 2001/060166 A1 discloses fermentation, lysis, and extraction of docosahexaenoic acid (DHA) from the marine algae Cypthecodinium cohnii and the potential use of macroalgae such as Rhodophyceae, Gigartinaceae, Gigartina stellata, and Chondrus crispus as sources of carrageenan and DHA for pet food. The non-used remains of the algae are combined with yeast in a process for making pet treats.
U.S. 2006/0241287 A1 discloses a method for using ionic liquids to extract and separate a biopolymer from a biomass. The biopolymer is dissolved in the ionic liquid and may then be separated from the ionic liquid. The process, and therefore the biomass, must take place in the substantial absence of water. Algae is cited in the publication as a suitable biomass source for chitin but no example of chitin extraction from algae biomass is provided and no conditions related to chitin extraction are suggested. The publication does not describe the extraction of lipids or materials other than biopolymers from biomass or the extraction of any substances from wet algae or other wet biomass.
U.S. 2006/0141556 A1 discloses a cell lysis method using microwaves in which an ionic compound additive, which may be an ionic liquid, is used to increase the efficiency of microwave heating during a cell lysis step to prepare nucleic acid for subsequent PCR. Organic ionic liquids such as dialkylimidazolium salts are suggested as potentially useful for the method. The amount of ionic additive used in approximately 10% by weight in the sample to be lysed and this amount is confirmed as insufficient to cause cell lysis.
U.S. 2008/0090284 A1 discloses a system for processing oil from algae. The system comprises an algae separator, a cell lysis device, an oil separator, and a biofuel reactor. No specific means of cell lysis is suggested nor is a suggestion regarding chemical vs. mechanical lysis provided.
U.S. 2009/0081742 discloses a method for processing algae in which steam is used to lyse algae cells. The system includes a bioreactor for synthesizing biodiesel from intracellular oil. The lysing process involves the mixture of steam with a concentrate of algae cells.
U.S. 2009/0170184 A1 discloses a system for growing and processing algae. The system comprises bioreactors for growing algae, a dewatering unit for concentrating algae, a cell lysis chamber, and a separator for separating lysis products. Algae cells in the lysis chamber are mixed with CO2 at a pressure greater than 1 bar. Pressure/phase changes of CO2 injected into the algae cells are used to rupture the cells.
U.S. 2009/0234146 A1 discloses methods for the direct transesterification and extraction of biolipids from biomass, including plants, yeast, and algae. Large numbers of possible ionic liquid/cosolvent combinations are suggested. All examples of the process involve drying the biomass and grinding it into a fine powder.
WO 2010/023136 ('136) discloses a process for producing liquid fuels from lipid-containing biomass, including algae, by: (i) providing the biomass in a dry or semi-dry form and (ii) dissolving said the biomass in an ionic liquid at a temperature of between 60° C. and 120° C. whereby a lipid phase and a hydrophilic phase are formed. The hydrophilic phase may contain cellulose, hemi-cellulose and dissolved protein. The ionic liquids are selected from a large number of organic or inorganic salts having melting temperatures of about 120° C. or less and include imidazolium cations combined with halides, C1-C6 carboxylates, C1-C6 alkyl sulfates, mono-and di-C1-C10 alkyl sulfosuccinates, mono- and di-C1-C10 ester sulfosuccinates, and mixtures thereof. Inorganic ionic liquids are preferred with ZnCl2 xH2O, x>2 most preferred, in part because biomass proteins in non-denatured (natural) form are soluble in the ionic liquid medium. The '136 publication does not exemplify the lysis method or disclose critical conditions such as durations of lysis and relative amounts of ionic liquid and biomass. No correlations are made between ionic liquids, algae, and conditions for lysis.
The aforementioned processes do not meet the need for an environmentally safe and economically viable process for producing biofuels, nutrients, and other useful products from algae biomass. Lysing algae by steam, microwaves, and mechanically induced pressure changes require relatively large amounts of energy. Chemical lysis methods often involve volatile organic chemicals or ionic detergents that interfere with subsequent separations. Drying algae to a powder requires energy for centrifugation, filtering, and/or heating. High temperatures during lysis and drying can denature proteins or degrade other desirable products. Unlike biomass obtained on land, harvested algae contains a large percentage of water. The present specification discloses methods and apparatus involving the use of certain hydrophilic ionic liquids to lyse algae cells. The ionic liquids and conditions disclosed are distinct from those useful for dissolving and/or processing dry biomass.
Lysis and extraction of algae cells by ionic liquids can provide an environmentally sound alternative to more energy intensive methods, but they are expensive and have only recently been shown to lyse wet algae concentrates at temperatures as low as 80° C. U.S. patent application Ser. No. 12/970,512, assigned to the same assignee as the present application, discloses the use of ionic liquid 1-butyl-3-methylimidazolium chloride to lyse suspensions of algae cells at temperatures of approximately 80° C. to 120° C. and to extract lipids from the resulting lysate. The lysate may also be processed to recover other materials from the algae. The ionic liquid is recovered for re-use by the addition of a salt to salt-out algal components and water.
The present invention provides methods and apparatus for processing algae at ambient or elevated temperatures using ionic liquids, efficient recovery of ionic liquid using a salting-out procedure, and recycling of salts and ionic liquid. The process ay be used to isolate a wide variety of materials from algae for use in biofuels, pharmaceuticals, nutraceuticals, foods, and other products.